As a method of judging a risk of cancer recurrence, a pathological evaluation method using Ki67 protein contained in cells extracted from cancer patients as a cancer marker is known. For example, there is a correlation between the proportion of the number of Ki67-expressing cells in the number of cells to be measured with the histopathological grade of cancer and the risk of cancer recurrence increases as the proportion of the number of Ki67-expressing cells is higher, which is described in Mark J Beresford, et al., Breast Cancer Research 2006, 8:216. Here, only the Ki67-expressing cells are stained using a reagent which specifically stains Ki67 in the cells so that the proportion of the number of Ki67-expressing cells in total cells is calculated.
Further, a method for judging a risk of recurrence including: analyzing the presence or absence of the expression of 21 gene clusters including ki67 gene; calculating a recurrence score; and classifying the results of the recurrence score into three stages (risk of recurrence is high, medium, or low) is described in N Engl J Med 2004; 351:2817-26.
In N Engl J Med 2004; 351:2817-26, a hazard ratio (HR) calculated using a statistical procedure is shown as an index showing the reliability of the classified results based on the recurrence score, however there is a further need for the judgment method in which the HR is improved.
On the other hand, a method for judging a risk of cancer recurrence using cyclin-dependent kinase (hereinafter also referred to as CDK) is described in United States Patent Application Publication No. 2009/246809. In this method, the risk of recurrence of cancer is judged by comparing a recurrence risk score which is calculated based on activity values and expression levels of two cyclin-dependent kinases (CDKs) with a predetermined threshold value.